1. Field of the Invention
The present invention relates to a heat resistant copolymer composition. More particularly, it relates to a heat resistant copolymer composition having good processability and impact resistance.
2. Description of the Prior Art
Acrylonitrile-styrene (AS) resins and acrylonitrile-butediene-styrene (ABS) resins have good molding properties, chemical resistance and impact resistance and are widely used as materials for, for example, automobile parts, electrical parts, business machine parts, etc. However, these resins have inferior heat resistance compared to polycarbonate and modified polyphenylene ether and are required to have better heat resistance.
Recently, to improve heat resistance, an AS or ABS resin further comprising maleimide monomeric units as a component for imparting heat resistance to the resin has been developed. Further, a heat resistant resin composition comprising a blend of the resin which comprises the maleimide monomeric units (e.g. N-phenylmaleimide-styrene copolymer) and a styrene-acrylonitrile copolymer is known from, for example, Japanese Patent Kokai Publication Nos. 98536/1982, 217535/1983 and 217537/1983.
The blend of the resin which comprises the maleimide monomeric units and the styrene-acrylonitrile copolymer is technically useful since the heat resistance of the composition can be easily controlled by changing the blend ratio of the two copolymers.
However, copolymers to be blended are often incompatible with each other. In such case, the effect of the copolymerization of maleimide monomer for the improvement of heat resistance is achieved to a lesser degree, and the obtained composition has poor balance of properties such as heat resistance, molding properties and resistance.